Method and means for surfacing solid bifocal lenses



M y 2, 1936- I A; couRMEi-TEs 2,040,242

METHOD AND MEANS FOR SURFACING SOLID BIFOGAL LENSES Filed May 25, 1932 Il f7 /7 25 NE 4 \uuuum INVENTOR Patented May 12, 1936 UNITED STATES PATENT OFFICE mn'rnon AND MEANS FOR SURFACING SOLID BIFOQAL LENSES Henry A. Courmettes, BrcoklymN. Application May 23', 1932, Serial No. 612,971

4 Claim.

face grinding of anumber of lenses upon their.

differently curved inner surfaces at one time,

requiring only one blocking for this operation; I

the parts used are capable of adjustments heretofore not used in the art.

The method being intended primarily for grinding the inner surfaces of the bifocal lens referred to, whereupon the said inner surfaces are inclined toward each other, consists particu I larly in; mounting or blocking a number of glass blanks upon their backs on the peripheral surface of a circular lens holder, the shank of which .is made to fit the spindle of surface grinding machines; surfacing the upper and corresponding inner bifocal surfaces of all the lenses on the lens holder by means of an annular grinding.

tool of' sufllcient diameter to/cover and grind part of each of the said surfaces; said annular tool being fitted with a device serving as a p'ivotal center of rotation, which also carries a seconda pivotal point used as a center of rotation for a second surfacing tool located directly under the annular grinder; surfacing the lower and corresponding inner bifocal surfaces of all the lenses, by means of a surfacing tool of such diameter as to reach and cover part of each lens and of such thickness as to pass between the revolving lenses and the larger annular grinding tool; maintaining the proper relation of position obtain a line of,

of the two grinding tools to junction of the two inner bifocal surfaces of the lens free from steps or ridges, by means of thetwo aforesaid grinding tools and an adjustable Q device secured thereto, 'servingas a double pivotal center of rotationand separating the two.

tools to the exact space required; and completing the surface grinding prowss while revolving the grinding tools'eccentrically to the'center of rotation of the lenses.

. Thesuperimposed grinding tools and the adjustable pivotal center being the means by which I the multiple and simultaneous surfacing is obtained.

Reference is made to the drawing herewith forming 'a part, of this invengon and in which similar numbers refer to simil parts throughout andinwhichi' rig. Us a sectional side view of the particular as possible; acircular surfacingtool 'form of lens for the grinding of which this invention is intended.

Fig. 2 is a face front elevation of a similar lens, showing the straight transversal line created by the similar outside surfaces and the trans- 5 versal downward curve created by unsimilar curves ground upon the inner surfaces.

Fig. 3 is a sectional side elevation of a lower 'circular matrix block serving as a glass blank rest, an upper circular lens holder with cement- 10 ing or blocking material upon a portion of its face, and the glass blanks secured thereto.

Fig. 4 is a top face view of the lens holder and lenses cemented thereto at regular intervals in a circular position.

Fig. 5 is a sectional side elevation of the lens holder showing the lenses in position for grinding, and the standard shaped shank.

Fig. 6 is asectional side elevation of the assembly in operation; showing the upper annular 20 I grinding tool, the adjustable pivotal center screwed thereto, the lower grinding tool, the glass blanks and the lens holder.

Fig. 'I is a-sectional side view of the device for rotating the two grinding tools upon one common axis and to maintain the proper separation of the said tools.

Fig. 8 is a sectional side elevation of a similar adjustable device, but of theball bearing tyn Glass blanks which have been previously 30 shaped by heating and pressing into a mould while in a molten state to approximately the form of the finished; surfaces of the lens as'in Figs. 1 and 2 are usedin this description of the method. 3

The blanks 8 Fig. 4 are placed face down upon a matrix block 5 Fig. 3 in a position giving closest contact of the surfaces 4 and 5 Fig. 3 to the block and in a circular position at regular intervals as shown in Fig.,- 4; eight of such glass blanks or '54 m/m diameter being possible at one time, de-

pending upon their curvatures and angles of the two fields l and 2 Fig. 2. A circular lens holder 1 shaped to conform to the contours of the lens blanks 8 and the matrix block 6, is'heated and the face of it covered with blocking pitch 9 on other cementing substance and applied while hot to the lens blanks. The lens holder I, lens blanks 8 and matrix block 6 are held together as in Fig. 3 until the. blocking cement BohflS cooled and 50 hardened to hold the blanks securely in place. The lens holder 1 is then set upon a surfacing spindle l0 Fig. 5,-preferablya self centering ball bearing spindle, turning as accuratelymnd true ll Fig. 6'

adjusting repeated if having a predetermined-curved grinding surface l2 and of such diameter as to-cause the edge i3 of the tool to reach the line of demarcation I4 on the glass blanks 8 when revolving eccentrically to the axis. l5 of the surfacing spindle I0, is laid upon the surfaces 5 of the lens blanks; this surfacing tool I l is provided with -a correctly centered pivotal hole I 6 into which the point I1 of the adjustable device l8 rests.- Then, an annular surfacing tool l9 Fig. 6, also of predetermined curvature and of diameter computed to grind the entire upper surface 4 of the lens blanks when revolving upon the same axis of rotation as that of the first surfacing tool II but eccentric to the axis l5 of the spindle I0, is laid over the smaller surfacing tool II and in contact with the lens surfaces 4; the pin 20 of the surfacing machine is lowered into the adjustable center I 8 and held rigidly at a measured distance from the axis I 5 of the surfacing spindle and in this'positionthe grinding proceeds, first with grinding material of medium grain until all surfaces are entirely roughed out; during the process close examination' reveals whether the surfaces meet evenly at their line of junction l4, if a ridge is left, an ad-- justment of the screw 2| to sink or raise the tool II is readily made, as necessary, by means of the hexagon nut 23 of the centering device |8;- the finer grinding materials are then used and the necessary until the lenses areready for polishing; this is done by applying a polishing material to the faces of the surfacing tools, being careful not and revolving same over the grinding process. A piece of glass 24 cemented in the center of the lens holder I is often a helpin maintaining the curvature and balancing the pressure on the surfaces 5 ground by the small surfacing tool;

During the process it use only one of the surfacing tools at the time;

this method lends itself to this use as well.

Instead of revolving the surfacing spindle as described,'the grinding process may be varied by maintaining the lens holder in a fixed position I and revolving the grinding tools by the upper pin surfacing machine, which is then secured and moved around eccentrically, to an upper driving axle. have a common pivotal and radial axis and therefore this method is also understood to come within'the claims of this inventio The thimble, member l8, shown in Figs. 6 and 7-, is understood to provide means for maintaining two superimposed lens surfacing laps in a common axis of rotation, first,- by its pointed pin I! which is held in the conical shaped center l6 of lap H through pressure imparted by pin ;20, sec-- nd, by its hollow shaped center 25 into which the rounded end of pin-20 rests, and third, by its circular threaded wall 2| which secures it to the upper lap 19. The pointed pin l1 provides the universaland pivotal motion for lap II, the

' broken line to overlap their edges the lenses exactly as in is sometimes necessary to- 9. member engaging said .viding a pointed pin serving as guide for one of In'this'case-the grinding tools still hollow shaped center 25 provides the universal and pivotal motion for lap I9, the threaded wall 2| provides means to adjustably secure member l8 to lap l9 relatively to the surfaces 4 and of the lenses 8; the center 25 and pin I1 having the same common axial center, as shown by vertical 26 in Fig. 7, provide the means to maintain a common axis of rotation for both laps II and I9, and the nut head 23 integral with member l8, serves to regulate said member in lap l9.

Although numerous variations of the forms of pivotal centers and shapes of grinding tools may be devised, I am anticipating those intended to obtain the same result, it being sufiicient that the two grinding tools have ;a common axis of rotation, that one of these be provided with an adjustable centering device supplying apivotal center for both tools, and that said adjustable centering device be provided with means to keep both tools at a correct and controllable distance from each other.

Having thus described my invention for the special grinding of the lenses referred to, I claim:

1. A device for maintaining two superimposed lens surfacing laps in a common axis of rotation and comprising i a universal bearing joint serving as pivotal center for one of said laps; a pointed pin serving as a pivotal center for the second lap, and means to adjustably secure said device relatively to the level of the grinding surfaces of the said laps.

2. A device to aid in surfacing solid bifocal lenses and to hold two lens-surfacing laps in a substantially common axis of rotation, consisting of a onepiece member shaped to comprise a pivot pin, an internal pivot center co-axial with said pivot pin, an external threaded wall, and a screwnut head, as set forth. v

3. A device to aid in surfacing the bifocal lens referred to and comprising, in combination; two

superimposed surfacing laps. having a common axis of rotation and independent pivotal centers; surfacing laps and pro the surfacing laps, an internal pivot center 00- axial with said pointed pin and serving as pivotal center for the second lap, an external screwthreaded wall to secure said member to one of the laps, and a screw-nut head to adjust said member into the said second'lap; and the abrading surface of the superposed surfacing'lap being annular in shape and spherical in curvature.

4. A device to aid in surfacing the 'solid bifocal lens referred to and comprising, in combination, twosuperimposed surfacing laps having a common-axis of rotation; and a member engaging the said laps and providing means to adjustably control the separation between the said laps relative to their grinding surfaces, said member also providing separate pivotal centers for both of said laps, as set forth. V

; HENRY A. COURME'I'I'ES. 

